Really allow NetworkAgent immutable updates to NetworkCapabilities

This patch completes commit bae105a5 to
really allow updates of immutable capabilities to NetworkCapabilities of
NetworkAgents by using satisfiedByImmutableNetworkCapabilities instead
satisfiedByNetworkCapabilities.

Bug: 64125969
Test: runtest frameworks-net
Merged-In: I9beeb623792f0ee31abcd4ba9d0ba2451304fb2e
Merged-In: Ifbdd005576b3f0fbf278ecec81ce3e4308c6276d
Merged-In: Id352fdb6da21a2150d3e8d062d7eba11878f6919
Merged-In: If3742ea0e2151b9b710eda2fed280c31f7960393
Merged-In: Icd8e328e3c810a644bfb83798bd42fed8dc70425

(cherry picked from commit a60c6eab)

Change-Id: I737494117d7f1e0198f0ad4d3c41019c9295fe09